The present invention relates to an aircraft propulsion unit, such as a jet engine, comprising a nacelle exhibiting fan cowls that can be closed and locked by a single operator.
An aircraft propulsion system comprises a nacelle surrounding a turbojet engine. For the purposes of maintaining the turbojet engine, the nacelle generally comprises two fan cowls articulated about pivoting axes which are substantially parallel to the longitudinal axis of the nacelle and disposed symmetrically on both sides of the support column by which the nacelle is suspended from the aircraft wing. Each fan cowl is movable between a closed position in which the fan cowl is disposed in the extension of the outer surface of the nacelle in such a manner as to cover the housing of the fan and an open position in which an operator can access the housing. The lower sides of the fan cowls situated in the bottom section of the nacelle are substantially contiguous in the closed position and are kept in this closed position (locked position) by locking devices distributed along the lower contiguous edges of the fan cowls.
It is important to be able to check that a fan cowl is in the locked position before the aircraft takes off. In fact, a fan cowl which is in the closed position but is not locked can be torn off in flight by scooping. Under the effect of its own weight—in the order of 60 kg—and due to the position of its pivoting axis, a fan cowl tends to move closer to its closed position, even though it is difficult for an operator to determine visually whether a fan cowl is in the closed position or in the locked position.
It is known for the nacelle to be fitted with visual detection devices designed to make it clear that the fan cowls are not in the locked position. Hence, it is known for a system such as that described in French Patent Application FR20130056508 to be used, said patent being filed on behalf of the applicant in this case. In the embodiment described in FIG. 8 of this application, the system enables the lower contiguous edges of the fan cowls to be spaced apart via a system of springs resting one against the other while said lower sides are not in the locked position.
A system of this kind is effective but the physical effort required of an operator in order to overcome the load generated by the spacing mechanism and to move the lower contiguous edges of the fan cowls closer to one another, so as to be able to position said fan cowls in the locked position, is substantial, even if it still conforms to the ergonomic standards defined for a single individual.